Synergistic effects lead to high thermoelectric performance of iodine doped pseudo-binary layered GeSb2Te4

Pseudo-binary layered compound IVVI-V2VI3 families show great promise for application in thermoelectrics. Herein, through introducing iodine in GeSb2Te4, several synergistic effects come into being and contribute to outstanding thermoelectric performance. The I Te donor-like defects suppress the hole carrier concentration from 5.72 x 1020 cm-3 to 2.80 x 1020 cm-3 . First-principles calculations reveal that iodine doping increases the band gap from 0.253 eV to 0.302 eV and contributes to valence band convergence. Seebeck coefficient value reaches up to 135.7 mV/K at 773 K, and the power factor values are entirely boosted in the whole temperature region, reaching a maximum value of 12.4 mW center dot cm-1 center dot K-2 in GeSb 2 Te 3.96 I 0.04 . Moreover, iodine doping simultaneously reduces the lattice and electronic thermal conductivity, leading to the greatly reduced total thermal conductivity from 2.89 W center dot m-1 center dot K-1 in pristine sample to 0.89 W center dot m-1 center dot K-1 in GeSb 2 Te 3.84 I 0.16 at 323 K. Finally, a maximum zT-1.12 at 773 K and an average zT-0.62 over 323-773 K are achieved in GeSb 2 Te 3.88 I 0.12 . This work puts forward an effective strategy to synergistically optimize phonon and carrier transport properties of pseudo-binary compounds through halogen doping, which may be effective in other similar material systems. (c) 2024 The Authors. Published by Elsevier B.V. on behalf of The Chinese Ceramic Society. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).